This invention relates to a method for controlling an internal combustion engine of a vehicle in order to reduce low frequency bouncing oscillations of the vehicle, which is a phenomenon known as xe2x80x9croad lopexe2x80x9d.
It is known that off-road vehicles, such as agricultural tractors can, when operated on roads in higher gears and at transport speeds, experience a bouncing condition known as xe2x80x9croad lopexe2x80x9d, wherein the vehicle oscillates with a frequency in the range between 1 and 3 Hz. A similar condition known as xe2x80x9cpower hopxe2x80x9d can result when a vehicle operates off road, at lower gears and at lower speeds. Various methods and designs have been proposed in attempts to solve this problem. For example, European patent application EP 1 022 160, published on Jul. 26, 2000 and assigned to the assignee of this Application, describes a wheel mounting disk which is intended to more accurately center a wheel and tire on a vehicle axle. However, such a wheel mounting disk has not completely eliminated road lope. U.S. Pat. No. 6,035,827, issued Mar. 14, 2000 to Heinitz et al., discloses a system wherein an engine speed signal is fed back to a characteristic function, and wherein an engine fuel quantity signal is operated on by an inverse transmission function to generate a compensated fuel quantity signal. However, the practicality of such a system is doubtful because it is believed to be difficult to extract the needed information from the feed back engine speed signal.
German Published, Non-Prosecuted Patent Application DE 195 37 787 A1 discloses a method for compensating bouncing oscillations. In that reference a signal expressing the wish of the driver is filtered through the use of a transmission element. The parameters of the transmission element, and thus its transmission behavior, are changed as a function of operating parameters while the internal combustion is operating. Furthermore, a subordinate rotational speed control is used for non-steady operation, which leads to a considerable number of application parameters.
Accordingly, an object of this invention is to provide a method and system for reducing road lope in a vehicle, such as an agricultural tractor.
A further object of the invention is to provide such a method and system which does not require tire adjusting or manipulation.
A further object of the invention is to provide such a method and system which does not require extracting information from an engine speed sensor.
These and other objects are achieved by the present invention, which is a method and system for controlling road lope in a vehicle having an engine driving wheels through a transmission having multiple gear ratios, and having a fuel control unit for supplying a variable amount of fuel to the engine in response to fuel control signals generated by an engine control unit. The method includes sensing vehicle acceleration with an accelerometer mounted on the vehicle and generating an acceleration signal in response to motion of the vehicle, generating time constant and torque gain values as a function of the transmission gear, generating an output torque value as a function of the acceleration signal, an engine torque, the time constant and the torque gain, and modifying fuel delivered to the engine as a function of the output torque value.